While hearing loss can have a variety of causes, including infection and some medications, its most prevalent cause is the simple act of aging. About 18 percent of the entire U.S. population are Baby Boomers—some 57 million people—who are now turning 60, and more of the population will continue to thrive and remain active until well into their 80s. Hearing usually holds steady until about age 50, starts to drop by age 60, and takes a more significant drop between age 70 and 80.

In fact about half of all men and women older than75 have age related hearing loss, said Gerald R. Popelka, PhD, a Stanford professor of otolaryngology and chief of Stanford Hospital & Clinics audiology program, at a presentation sponsored by Stanford Hospital Health Library.

Normal hearing receives frequencies from about 20 Hz (a very low buzz) to about 20,000 Hz (a very high squeal). Human speech falls mostly in the range of 250-6,000 Hz. For most people, hearing loss sneaks up gradually over the years. They start to drop the higher frequencies, picking up missing bits of conversation by context or visual signs. Phones are particularly notorious for dropping both the higher and lower ends of auditory frequencies.

Part of the Aging ProcessHearing loss does affect men and women differently, with a 20-year difference in rate of decline, he added. That means an 80-year-old woman might have the hearing of a 60-year-old man, which can add to communication problems between spouses and family members. Studies have shown that the age of hearing loss has remained consistent in the 60-year-old age group for the past 30 years, so lifestyle changes and Boomers’ love of loud music is not a major factor in terms of when onset occurs.

Age-related hearing loss cannot be corrected through surgery or medication, said Dr. Popelka, who helped invent the first digital hearing aid in the 1980s. Because hearing loss takes place in the hair cells, the cells deep in the inner ear that connect to nerves sending sound messages to the brain, the damage is permanent and, so far, irreversible.

But when hearing starts to decline, an almost-inevitable aspect of aging, many people hesitate to use a hearing aid. If their sight were failing, most people wouldn’t hesitate to get glasses, he added.

“The vast majority of hearing loss is simple age related and will worsen progressively,” he said. “There are no surgical or medical interventions for the 25 percent of people in the U.S. who have hearing loss caused by this type of damage. For most, the answer is a hearing aid.”

Customized DevicesA hearing aid is a miniature electronic device that amplifies sound. Most are made up of the same basic components—a microphone, a battery, a loudspeaker and a computer—that must be custom adjusted for each user. Listening to complex and changing sounds coming from different directions, blocking out unnecessary background noise, or interpreting environmental sounds involve a complex system of controls.

Hearing aids, which are devices regulated by the FDA, are not the same as hearing assistance devices or personal sound amplification systems. Amplifying a conversation without compensating for these other factors doesn’t make it easier to understand a conversation, he said. Hearing aids involve a computer chip that must be customized for each patient: These adjustments are very complex and require the skill of an audiologist.

Advances in technology have not only made hearing aids increasingly smaller but have added new features and address many of the problems of earlier models. The whistling sound many users complained about has been eliminated. Many people now prefer a “mini” version of a BTE (behind the ear), which is virtually invisible. Since BTE models have an open fit, the ear canal is not blocked and all sounds can come through naturally.

“They can be connected wirelessly to the TV, cell phone, GPS, car, or Internet. They can distinguish background noise and music from speech and automatically modify their settings accordingly,” said Dr. Popelka. “The controls are no longer manual. They automatically can adapt and adjust their settings. Sounds sound natural.”

BTE models also come in bright colors, which can act as a fashion statement and make them easier to find if they are dropped since they are so small. Many models are smaller than a dime.

Improved TechnologyAnother option is a disposable device that is fitted completely inside the ear canal. This style is totally invisible but can muffle sounds, and some users say that their ear feels full. This style must be inserted by a professional, and must be replaced every few months.

“Today’s hearing aids are physically comfortable, easy to put on, almost invisible, and have excellent performance,” said Dr. Popelka. “In fact over the past 10 years there’s been a reversal in usage, and now more people prefer the over the ear style. It’s a dramatic change.”

He also noted an increase of double usage—wearing hearing aids in both ears. Using two devices allows for three-dimensional acoustics, making it easy to identify the speaker or source of sound in an ambient or noisy environment. A device worn around the neck can program the devices to communicate with each other and be adjusted accordingly. A remote microphone or smartphone app can be used to listen to the television or to amplify sounds in public places. For example, many theaters and performing arts venues feature a telecoil loop system so users can hear through their hearing aids perfectly from any seat. Those without a wireless hearing aid can link into the system with earphones supplied by the facility.

Dr. Popelka addressed concerns about the cost of hearing aids, which often are not reimbursed by insurance companies. The cost is related to demand, he said, and the expertise required to adjust each hearing aid to its user. FDA-approved manufacturers offer similar features, he added, but be leery of a facility that offers only one brand and select a place with professional audiology services, including diagnostics, evaluation, and follow-up care.

“The technology has improved immensely. There is less need for hearing aids to get smaller since the focus now is on adding in more features,” Dr. Popelka said.

While today’s hearing aids feature noise cancellation, automated controls, wireless configurations, internal memory, and water resistance, the future may hold strategies for preventing hearing loss in the first place. Research in Dr. Popelka’s department is looking to prevent hair cell damage as a side effect of some antibiotics and of chemotherapy. His associates also are exploring the use of stem cells and gene therapy to restore hearing.

“Age-related hearing loss affects quality of life,” he said. “Studies show a dramatic improvement in the quality of life when hearing is improved.”

About the SpeakerGerald Popelka, PhD, is chief of the Division of Audiology and co-director of the Stanford Balance Center. His work focuses on refining digital hearing devices and developing strategies to assess the hearing-related effects of antibiotics and pharmaceuticals used to treat cancer. He is a faculty advisor at the Stanford Center on Longevity and is a board member of the Baker Institute for Hearing Impaired Children

Before coming to Stanford in 2004, Dr. Popelka was a faculty member for 24 years at Washington University in St. Louis and served as head of audiology at Central Institute for the Deaf, an affiliated research institution. He received a master’s degree in audiology from Kent State University, a PhD from the University of Wisconsin, Madison, and completed his research fellowship at UCLA.